Struggling Ricky Ponting ruled out his chances of playing in next year's Ashes in England unless he breaks his dismal run of form in the series against South Africa.

The former Australia skipper, who turns 38 next month, has failed in three innings against the Proteas, chopping a Dale Steyn delivery onto his stumps to fall for 16 in another cheap dismissal on Saturday.

Pressure is building on the 167-Test veteran ahead of Friday's third and final Test against South Africa in Perth.

Ponting said he was a realist and knew that if he did not start scoring runs then he "definitely" would not be in England for the Ashes in July and August.

"I am a realist. I live in the real world and I know that if I am not getting runs then there's no chance at all of even playing the summer out, so I definitely won't be in England," Ponting told the Nine Network.

"But we'll wait and see what happens at the end of this game. I am looking forward to getting a good win here and then we'll see how we go for Perth."

Ponting has spoken in the past about his burning motivation to keep on playing after leading Australia to back-to-back Ashes series defeats before Michael Clarke took over the captaincy.

Ponting, who has scores of 0, 4 and 16 in the ongoing series against South Africa, said he had not spoken to the selectors about his place in the Australia side, but expected a "conversation" with them shortly.

"I haven't spoken to the selectors about my immediate future and they haven't spoken to me about it either," Ponting said.

"I'm sure that conversation is going to come probably in the near future, but nothing's happened just yet."

Ponting, who ranks second behind only India's maestro Sachin Tendulkar for most runs scored in Tests, said he was looking to be more assertive if given further opportunities to play for Australia.

"Form-wise, I've been a bit tentative, certainly in the first innings in Brisbane it was a tentative shot," he said.

"Yesterday afternoon (Saturday) was a tentative shot and that's not the normal way that I play.

"I have no illusions or disillusions about where my cricket is at, it's just a matter of working hard. Then hopefully when I get a chance to bat in the middle I'm a bit more assertive than I have been in the last couple of games."

Ponting may be helped by poor form among the Australian top order, with newcomer Rob Quiney unlikely to play in Perth after a pair of ducks in the second Test.